Filtration structure for fluid flow radially through cylindrical configuration defined by stack of serrated wafers

ABSTRACT

This invention is a filtration structure characterized by radial fluid flow through the wall of a cylindrical configuration that is established by a stack of serrated annular wafers which are constrained for slight axial movement with respect to each other, for the establishment of two conditions. In one condition, the wafers are axially compressed into snug contact under spring bias to establish a labyrinth of radial passages for fluid flow at a selected pressure. In the other condition, the axial compression of the disks is relieved and the disks are slightly separated by back flushing under an elevated pressure in such a way that cleansing is freely effected by reverse fluid flow.

RELATED APPLICATIONS BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the filtration of contaminated waterand industrial waste fluids, and to systems for filtration of finelydispersed contaminants and waste products.

The present application is a continuation-in-part of application Ser.No. 07/588,572, filed Sep. 21, 1990 in the name of Sohail Zaite, nowabandoned.

2. Background of the Invention

There have been proposed a variety of filtration structurescharacterized by fluid flow radially through the porous wall of acylindrical configuration that is established by a stack of annularwafers. These wafers generally are characterized by opposed reticulatedfaces that establish a radial labyrinth of passages through which thefluid can pass between the interior and exterior surfaces of thecylindrical configuration. Such prior structures typically have beenconstituted by disposable packaging or have been prone to cloggingproblems, particularly when very fine particles have been involved.

SUMMARY OF THE INVENTION

The primary object of the present invention is to provide a filtrationstructure characterized by fluid flow radially through the wall of acylindrical configuration that is established by a stack of serratedannular wafers which are constrained for slight axial movement withrespect to each other for the establishment of two conditions. In onecondition, the wafers are axially compressed into snug contact underspring bias to establish a labyrinth of radial passages for fluid flowat a selected pressure. In the other condition, the axial compression ofthe disks is relieved and the disks are slightly separated by backflushing under an elevated pressure in such a way that cleansing isfreely effected by reverse fluid flow.

Preferably, the wafers are characterized by serrations which are skewedto intersect diameters through the center of the wafer at a selectedangle. Preferably a plurality of columns of such wafers operate within atank having two chambers that are separated by a hermetic plate. Thecolumns are located within a first chamber and feed through ports in theplate into the second chamber. The arrangement is such that radial flowoccurs into the outer peripheries of the tubular configurations in thefirst chamber, separation of impurities occurs in the intersticesbetween the wafers, and axial flow of cleansed effluent occurs from theinterstices into the interior of the columns and thence into the secondchamber. The arrangement is such also that back flushing occurs from thesecond chamber through the interiors of the cylindrical configurationsand from their external peripheries.

Other objects of the present invention will in part be obvious and willin part appear hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and objects of the presentinvention, reference is made to the following detailed description, inreference to the accompanying drawings wherein:

FIG. 1 is a perspective view of a water purifier embodying the presentinvention;

FIG. 2 is a broken away cross section of the purifier of FIG. 1, withparts omitted for clarity;

FIG. 3 is a broken away elevation of a component of the purifier ofFIGS. 1 and 2;

FIG. 4 is a perspective view of a broken-away stacked wafersub-assemblage of the purifier of FIGS. 1 and 2;

FIG. 5A is a partly broken away, enlarged detail cross-sectional view ofa portion of a wafer of FIG. 4;

FIG. 5B is a partly broken away, enlarged detail cross-sectional view ofanother portion of the wafer of FIG. 4;

FIG. 5C is a perspective view of a fragmentary detail of the wafer ofFIGS. 5A and 5B;

FIG. 5D is a plan view of the wafer of FIGS. 5A and 5B;

FIG. 5E is a broken-away plan view of FIG. 5D, enlarged to show addeddetails; and

FIG. 5F is a grossly magnified, broken-away cross-section of the waferof FIGS. 5A and 5B.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to FIGS. 1, 2, 3 and 4, the illustrated filtration unit20 is shown as comprising a pressure vessel 22. Within this vessel are alower chamber 24 and an upper chamber 26 which are separated by an upperplate 28. Positioned near the bottom of lower chamber 24 is a lowerplate 30 which is hung from and secured to upper plate 28 by tie rods32. Tie rods 32 have threaded extremities on which are turned suitablehex nuts 34. Extending between the plates are a series of paraxialtubular, filtration columns 36, each of which is constituted by a stackof thin, annular, plastic wafers 37. The opposite faces of the wafersare serrated in a manner to be described more specifically below.

As shown in FIG. 4, the inner profiles of these wafers snugly fit onto avertical guide 38 that consists of three rigid planar ribs 40, 42 and 44which are equiangularly disposed. In other words, in cross section,adjacent ribs are angularly spaced at 120° with respect to each other.The lower extremity of each vertical guide 38 is affixed by bonding orwelding to a collar 46. The upper extremity of each vertical guidesnugly extends through an opening in upper plate 28. Extendingdownwardly from collar 46 is a pin 48 which projects through and isreciprocable within an opening 50 in lower plate 30. A helical spring 52envelops pin 48 and is compressed between collar 46 and lower plate 30.

The arrangement is such that an aqueous flow into lower chamber 24through an entrance port 54 permeates each column 36 peripherally, anddeposits any dispersed particles in the interstices defined by theserrations at the surfaces of the wafers. This flow continues into theinterior of column 36, upwardly into upper chamber 26, and outwardlyfrom exit port 56. The system is cleansed by backwashing through a flushport 58 at an elevated pressure which causes the wafers to separateagainst the bias of spring 52 and the particulate agglomeration at thefaces of the wafers to dislodge for flushing through an outlet. A drain60 is provided at the bottom of vessel 22 for residual sludge and thelike.

EXAMPLE

The geometry of the wafers are shown in FIGS. 5A to 5F. As indicatedabove compressed stacks of these wafers constitute tubular filteringelements that are critical to the present invention. These wafers aremanufactured to very tightly controlled tolerances.

As shown in FIGS. 5A and 5B, dimensions 10A and 10B (0.00322 and0.00995) are the passage widths at the inlet and outlet diameters,respectively. Dimensions 11A and 11B (0.00252 and 0.00602) are thepassage depths at the inlet and outlet diameters, respectively. As shownin FIG. 5C, dimensions 10C and 11C (0.00425 and 0.00509) are the landingwidths at the inlet and outlet diameters, respectively. As shown in FIG.5E, the passages are equally distributed on the annular area surfaces atan angle 11E (18° to 28° ) with respect to a diameter line through thecenter of the wafer. As shown in FIGS. 5A and 5B, the passages defineequilateral, triangular, cross-sectional contours. The passages aremolded into both faces of the wafer, which has a thickness of from 0.020to 0.040 inch. Preferably, the wafers are composed of a high densitypolymer, particularly, a high density polypropylene, polycarbonate,fluoropolymer, nylon, kadel or radel.

In one example of the illustrated embodiment, each wafer is 0.032 inchthick and has an outer diameter of 1.375 inches and an inner diameter of1 inch. The vessel is approximately 19 inches in diameter. The wafercolumns include several hundred randomly oriented wafers each and theguides are approximately 20 inches long.

Reticulation sizes are the critical factor in determining the largestparticle allowed to pass. Hence, the smaller the reticulation size, thehigher the filtering effect. With reference to FIGS. 5A to 5F, filteringeffects of 10 micron, 20 micron, 30 micron and 40 micron are shownbelow. Columns, in various embodiments, have different numbers ofelements, which correspond to the rate of flow required. Table 1 showsflow rates corresponding to various numbers of columns, elements andvessel sizes.

                  TABLE I                                                         ______________________________________                                        FLOW RATE M.sup.3 /HR.                                                        NO. OF NO. OF                             VESSEL                              COL-   ELE-     10      20    30    40    DIA.                                UMNS   MENTS    MIC.    MIC.  MIC.  MIC.  (in.)                               ______________________________________                                         1     300       2       5       7.5                                                                               10    4                                   3     500       5        12.5                                                                                18.5                                                                               25    6                                   6     300      12       30    45    60   10                                   6     500      20       50    75   100   10                                  12     300      25       60    90   120   12                                  12     500      35       90   135   180   12                                  18     500      60      150   225   300   14                                  36     400      90      225   337   450   16                                  36     500      115     300   450   600   16                                  60     400      150     400   600   800   20                                  60     500      200     500   750   1000  20                                  ______________________________________                                    

OPERATION

Operation is as follows in reference to pressure vessel 20, serviceinlet valve 54, product outlet valve 56, drain valve 60, backflush inletvalve 58, backflush outlet valve 59, and pressure gauges (not shown).Liquid to be filtered enters the vessel at a pressure of 40-100 psi. Byvirtue of this pressure, the liquid is forced through the waferinterstices and through their interiors to the outlet chamber. Helicalspring 52 is sufficiently strong to maintain tight contact. between thewafer when the liquid is at this pressure. This portion of the operationcontinues until the differential pressure between the inlet and outletchamber exceeds 20 psi. At this point, a backwash cycle begins.Backwashing is carried out manually or automatically. In the automaticmode, an initiation signal from differential pressure switches at theinlet and outlet valve activates the sequence of operations shown belowin Table II.

                                      TABLE II                                    __________________________________________________________________________                                               DURATION                           STEP                                                                              OPERATION                                                                             INLET                                                                              OUTLET                                                                              AIR VENT                                                                             BACK FLUSH                                                                            DRAIN                                                                              (mins.)                            __________________________________________________________________________    1   Preparation                                                                           OPEN CLOSE OPEN   CLOSE   CLOSE                                   2   Service OPEN OPEN  CLOSE  CLOSE   CLOSE                                   3   Backwash                                                                              CLOSE                                                                              CLOSE CLOSE  OPEN    OPEN 2.0                                4   Rinse   OPEN CLOSE CLOSE  CLOSE   CLOSE                                                                              0.5                                __________________________________________________________________________

To ensure that the backwash cycle is initiated and completed, a controlpanel (not shown) annunciates the following: (1) indicator lightilluminates showing high delta in pressure; (2) delayed flushingoperation resumes after allowing the closure of valves 54, 56 and 60;(3) cycle indicator light (BACKWASH-ON) illuminates and remains "ON"during the timed cycle (0-2 minutes); (4) when backwash cycle ends, adelayed step takes place (RINSE CYCLE); (5) indicator light goes onwhile valves are changing status; (6) after 0.5 minutes of rinse cycle,the system returns to service cycle.

In the manual mode operation, the above sequences are carried out by anoperator through the initiation of system shutdown and hand operation ofthe various valves in a sequence analagous to the one described above.

The present invention thus provides a unique design of a filteringelement made from polypropylene, polycarbonate, flouropolymer, nylon,kadel or radel having specially designed passageways which act as afiltering labyrinth when stacked on top of each other. These passagewaysare sized for filter ratings of 10 micron, 20 micron, 30 micron and 40micron. The filter system has a unique spring loading effect whichallows successful backwash of the filtering elements. Backwashing: for a10 micron rating is characterized by flow rates varying from 2 M³ /Hr to200 M³ /Hr; for a 20 micron rating is characterized by rates varyingfrom 5 M³ /Hr to 500³ /Hr; for a 30 micron rating is characterized byflow rates varying from 7.5 M³ /Hr to 750 M³ /Hr; and for a 40 micronrating is characterized by flow rates varying from 10 M³ /Hr to 1000 M³/Hr.

What is claimed is:
 1. A filtration structure comprising:(a) at leastone column of discrete annular wafers; (b) each wafer having an exteriorprofile and an interior profile; (c) each wafer being composed of adimensionally stable polymer; (d) faces of said wafers havingserrations; (e) a guide projecting through the interior profiles of saidwafers; (f) said guide having ribs in contact with said interiorprofiles; (g) said wafers defining a tube having an exterior surface andan interior surface; (h) said exterior surface and said interior surfacebeing adapted to communicate through interstices defined by saidserrations; (i) said interstices serving as a filter for a liquidflowing at an operating pressure between said exterior surface and saidinterior surface; (j) a spring connected with said wafers and said guidesuch that said wafers are capable of movement along said guide betweentwo conditions, the first condition being intimate contact under springpressure, and the second condition being slight separation when saidspring pressure is countered by fluid pressure greater than a givenfluid pressure.
 2. The filtration structure of claim 1 wherein saidserrations angularly intersect diameters of said wafers.
 3. Thefiltration structure of claim 2 wherein said serrations angularlyintersect diameters of said wafers at angles ranging from 18° to 28°. 4.The filtration structure of claim 1 wherein said polymer is a highdensity polymer selected from the class consisting of polypropylene,polycarbonate, fluoropolymer, nylon, kadel and radel.
 5. The filtrationstructure of claim 1 wherein said polymer is high density polypropylene.6. A filtration system comprising:(a) a pressure vessel having a firstchamber and a second chamber; (b) a plate separating said first chamberand said second chamber; (c) a plurality of filtration columns in saidfirst chamber; (d) each of said filtration columns defining an exteriorperiphery communicating with said first chamber and an interiorperiphery communicating with said second chamber; (e) each of saidcolumns comprising a stack of annular wafers; (f) at least one column ofdiscrete annular wafers; (g) each wafer having an exterior profile andan interior profile; (h) each wafer being composed of a dimensionallystable polymer; (i) faces of said wafers having serrations; (j) a guideprojecting through the interior profiles of said wafers; (k) said guidehaving ribs in contact with said interior profiles; (1) said exteriorperiphery and said interior periphery being adapted to communicatethrough interstices defined by said serrations; (m) said intersticesserving as a filter for a liquid flowing at an operating pressurebetween said exterior surface and said interior surface; (n) a springconnected with said wafers and said guide such that said wafers arecapable of movement along said guide between two conditions, the firstcondition being intimate contact under spring pressure, and the secondcondition being slight separation when said spring pressure is counteredby fluid pressure greater than a given fluid pressure; (o) during saidfirst condition said wafers being in an arrangement that is favorablysuitable for filtering fluids and during said second condition saidwafers being in an arrangement that is favorably suitable for thecleansing of contaminated wafers.
 7. The filtration system of claim 6wherein said serrations angularly intersect diameters of said wafers. 8.The filtration structure of claim 7 wherein said serrations angularlyintersect diameters of said wafers at angles ranging from 18° to 28°. 9.The filtration structure of claim 6 wherein said polymer is a highdensity polymer.
 10. The filtration structure of claim 6 wherein saidpolymer is high density polypropylene.
 11. A filtration systemcomprising:(a) a pressure vessel having a first chamber and a secondchamber; (b) a plate separating said first chamber and said secondchamber; (c) a plurality of filtration columns in said first chamber;(d) each of said filtration columns defining an exterior peripherycommunicating with said first chamber and an interior peripherycommunicating with said second chamber; (e) each of said columnscomprising a stack of annular wafers; (f) at least one column ofdiscrete annular wafers; (g) each wafer having an exterior profile andan interior profile; (h) each wafer being composed of a dimensionallystable polymer; (i) faces of said wafers having serrations; (j) a guideprojecting through the interior profiles of said wafers; (k) said guidehaving ribs in contact with said interior profiles; (l) said exteriorperiphery and said interior periphery being adapted to communicatethrough interstices defined by said serrations; (m) said intersticesserving as a filter for a liquid flowing at an operating pressurebetween said exterior surface and said interior surface; (n) saidserrations angularly intersecting diameters of said wafers at anglesranging from 18° to 28°; (o) a spring connected with said wafers andsaid guide such that said wafers are capable of movement along saidguide between two conditions, the first condition being intimate contactunder spring pressure, and the second condition being slight separationwhen said spring pressure is countered by fluid pressure greater than agiven fluid pressure; (p) during said first condition said wafers beingin an arrangement that is favorably suitable for filtering fluids andduring said second condition said wafers being in an arrangement that isfavorably suitable for the cleansing of contaminated wafers.
 12. Afiltration structure comprising:(a) at least one column of discreteannular wafers; (b) each wafer having an exterior profile and aninterior profile; (c) each wafer being composed of a dimensionallystable polymer; (d) faces of said wafers having serrations; (e) a guideprojecting through the interior profiles of said wafers; (f) said guidehaving ribs in contact with said interior profiles; (g) said wafersdefining a tube having an exterior surface and an interior surface; (h)said exterior surface and said interior surface being adapted tocommunicate through interstices defined by said serrations; (i) saidinterstices serving as a filter for a liquid flowing at an operatingpressure between said exterior surface and said interior surface; (j) aspring connected with said wafers and said guide such that said wafersare capable of movement along said guide between two conditions, thefirst condition being intimate contact under spring pressure, and thesecond condition being slight separation when said spring pressure iscountered by fluid pressure greater than a given fluid pressure; (k)during said first condition said wafer being in an arrangement that isfavorably suitable for filtering fluids and during said second conditionsaid wafers being in an arrangement that is favorably suitable for thecleansing of contaminated wafers; and (l) oscillation means for causingsaid movement between two said conditions.
 13. A filtration structurecomprising:(a) at least a column of discrete annular wafers; (b) eachwafer having an exterior profile and an interior profile; (c) each waferbeing composed of a dimensionally stable polymer; (d) faces of saidwafers having serrations; (e) a guide projecting through the interiorprofiles of said wafers; (f) said guide having ribs in contact with saidinterior profiles; (g) said wafers defining a tube having an exteriorsurface and an interior surface; (h) said exterior surface and saidinterior surface being adapted to communicate through intersticesdefined by said serrations; (i) said interstices serving as a filter fora liquid flowing at an operating pressure between said exterior surfaceand said interior surface; (j) spring means connected with said guideand said wafers such that said wafers are capable of movement along saidguide between two conditions, the first condition being intimate contactunder spring pressure, and the second condition being slight separationwhen said spring pressure is countered by fluid pressure greater than agiven fluid pressure; (k) during said first condition said wafers beingin an arrangement that is favorably suitable for filtering fluids andduring said second condition said wafers being in an arrangement that isfavorably suitable for the cleansing of contaminated wafers; (l)oscillation means for causing said movement between said two conditions;(m) said movement being related to the spring constant of said springand the distance the wafers travel between said first condition and saidsecond condition.